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Skimming through Promethease, I also find I have gene variants that raise my IQ by seven points. In this regard I am not particularly special, since 30 percent of people have the variant that confers four extra IQ points and 47 percent share the variant that adds three. People who don’t have these specific variants may well have versions of genes that boost their IQs in other ways.
Is the information useful?
Most people don’t need genetic testing to find out whether they are well-thatched white males who can digest milk. Confirming the obvious is gratifying, but genetic testing is supposed to offer access to the unseen future.
Since gene hunters generally try to figure out how heredity correlates with disease, the gene testing companies and Promethease produced a lot of information about how my genes might contribute to illness. In my case, it looks like it was a good idea to quit my three-pack-a-day cigarette habit 23 years ago. According to Promethease, I have several gene variants that significantly boost my chances of lung cancer, accelerated lung decline, and congestive obstructive pulmonary disease. Pathway Genomics confirms this result, noting that “your genetic profile suggests that you may be vulnerable to lung cancer.” I also have a variant that correlates with staying addicted if one becomes a smoker, which makes me wonder about a possible willpower gene hiding somewhere.
Cardiovascular disease risk is particularly interesting to me since my father died of a heart attack at age 70 and my mother, who suffered several heart ailments, died of a stroke at the same age. Heart disease is the leading cause of death in the United States: According to the American Heart Association, 830,000 Americans died of cardiovascular disease in 2006, some 425,000 of them from coronary artery disease. So it’s not surprising that I, like many people, have genes conferring some risk of heart disease.
Promethease finds that I have an SNP that increases my chances of coronary artery disease by 50 percent above average. Pathway Genomics measures 12 different markers for coronary artery disease and 11 gene variants associated with the risk of heart attack. The results suggest I am somewhat more susceptible than average to both. 23andMe tests for only one variant, which indicates that my risk of heart attack is slightly below average, at 20.9 out of 100 Caucasian males, whereas the average is 21.2 out 100. All three platforms find that I am at greater risk than average for experiencing atrial fibrillation, a heartbeat characterized by a fast irregular rhythm.
The differences in reported results between the companies arise not from inaccuracies but from their selection of studies to include in their analyses and their interpretation of the research. In any case, a 64-slice CT heart scan a few years ago showed that I had no sign of significant coronary blockages. Also, my total cholesterol level is 167 milligrams per deciliter, well below the 200 milligrams per deciliter threshold that increases heart disease risk.
What other genetic flaws did Promethease suggest? I have one copy of a gene variant that increases my relative risk of type 2 diabetes by 10 percent; I also have two copies of an allele that increases my chances of type 1 diabetes to 20 times the average. That sounds bad, but recent tests show that my blood glucose levels are well within the normal range, indicating that I don’t have diabetes.
My diabetes results illustrate an important concept: There is no single gene for such common ailments as heart disease, diabetes, or cancer. Instead, hundreds of genes combine with influences from the environment to either increase or reduce risks. As the saying goes, “Genes load the gun; the environment pulls the trigger.”
The more useful information that gene scanning can provide today is how we will likely react to various pharmaceuticals. “Drug response can be predicted accurately for more than a dozen drugs,” noted National Institutes of Health Director Francis Collins in the April 2010 issue of Nature. For example, 23andMe, Pathway Genomics, and Promethease all suggest that I would respond strongly to the blood thinner warfarin, which would mean that, should I ever need it, my physician should probably aim to stabilize me at a lower dose than average. By contrast, all three sources report that I should respond typically to the blood-thinning drug Plavix. In March the FDA updated Plavix’s label to inform physicians that there is now a genetic test to determine how patients will respond to it. Given my genetic risks for heart disease, Pathway Genomics reports the good news that people with my “genetic markers receive significantly greater benefit from intensive statin therapy (such as Lipitor) than people who do not have these markers.”
But in general, the results of current tests are probabilistic calculations based on a selection of low-risk susceptibility alleles. The right way to think about the current direct-to-consumer genotype screening tests is that they are a preliminary technology. They offer supplementary, not dispositive, information about various health risks. The tests are not perfect, but they are the beginning of the process through which consumers, physicians, and purveyors will learn how to better interpret and use genetic information over time. The only real response to many disease risks right now remains that hoary but correct advice to eat your vegetables, lose weight, exercise more, and not smoke.
What about Alzheimer’s?
Alzheimer’s disease envelops us in a fog of forgetting, gradually stealing our memories, minds, and identities. It robs us of our dignity, leaving us a helpless burden on our families. The prospect of Alzheimer’s disease is so frightening that two prominent researchers who have had their genomes scanned—James Watson, co-discoverer of DNA’s structure, and Steven Pinker, a cognitive psychologist at Harvard—declined to learn what their gene tests have to say about their risk of it. Specifically, they didn’t want to know if they carry copies of the APOE4 allele, which boosts the odds that a person will eventually get Alzheimer’s to as much as 20 times the average. (More happily, recent research suggests that people carrying APOE4 alleles have better memories in their youth than those who carry the APOE3 variant.)
Unlike Watson and Pinker, I do want to know. Not all gene screening companies include APOE4 testing, but Pathway Genomics does. The good news is that my failing memory is not due to APOE4; I have inherited two copies of the more common APOE3 variant, which suggests that my lifetime risk of Alzheimer’s disease is average. Of course, there are other gene combinations that can increase or decrease my risk.
Back in 1999, as APOE testing was becoming more widely available, a panel of bioethicists convened at Stanford University concluded that Alzheimer’s testing was inappropriate for most individuals. The bioethicists were concerned about the “impact of knowing one’s own genetic susceptibility to an incurable disease.” In particular, they were afraid that consumers would “make significant life decisions based on a misunderstanding of risk estimates.” They also feared that insurance companies might use such test results to discriminate against people in issuing and setting rates for health and life coverage.